Spacetime

Could someone please explain spacetime to me while being as simple about it as possible? I know what spacetime is, but I would like to have a better understanding of the concept if one could relate it do everyday events and give such examples.

If you can help, I would most appreciate it! ^_^

Well, you can't very well teleport, now can you? It takes time to move in a 3 dimensional space, and even light is subject to this. Hence, spacetime.

Hmmm its in Back to the Future, and in Heroes. I don't get it either.

The best explanation I've ever seen is A Brief History of Time by Stephen Hawking.

It's an awesome book, and explains quite a bit about general relativity.

As for what spacetime is, it's, well, space and time. The two things are the same is the gist of it. Time is a dimension, just like height and width.

There's more to it than that, but Sir Stephen does a much better job of explaining it than I ever could.

Urgh, PLEASE don't make me bust out a tesseract all up in here!

That would be using the fourth spacial dimension, which is different from time which is simply like a fourth dimension.

Originally Posted by GDwarf

That would be using the fourth spacial dimension, which is different from time which is simply like a fourth dimension.

Please, my brain hurts already, and I'm the one that brought it up.
Can we talk about Lorentzian wormholes, plox?

If you want more information about it, I'd suggest "The Terrible Truth About Time," in the Horrible Science series by Nick Arnold. It's a simplified way of explaining all about time, but it goes into a reasonable ammount of detail.

It's a Kid's Book by the way.

read what scientists say, but always remember this: "almost every non-mathematical science has no theorems, but conjectures"... meaning: "what we believe today might not be the same thing we will believe in the near future", this is specialy true in phisics...

Newton, Einstein, Hawking... all of them are or were unable to demonstrate what they believe is the truth... almost every scientific fact is either a definition (which is giving names to things we don't know, making them more scientificly friendly by doing this. For example: "gravity"... everyone knows what gravity is right?... well actually no. Nobody knows for sure what gravity is, we know some of it's effects, and we know it's name, but we don't know why we always fall to the ground again every time we jump, we call that gravity, but still we don't know why...) or a conjecture (following the example: the existence of a particle that communicates the effect of gravity is conjectured)...

Is incredible the power science has to convince people that everything scientists say is absolutely right, however most scientific facts are probably false... everything is pure conjectures

"Science is forever tentative and human understanding is forever limited."

Originally Posted by Rock lee

read what scientists say, but always remember this: "almost every non-mathematical science has no theorems, but conjectures"... meaning: "what we believe today might not be the same thing we will believe in the near future", this is specialy true in phisics...

Newton, Einstein, Hawking... all of them are or were unable to demonstrate what they believe is the truth... almost every scientific fact is either a definition (which is giving names to things we don't know, making them more scientificly friendly by doing this. For example: "gravity"... everyone knows what gravity is right?... well actually no. Nobody knows for sure what gravity is, we know some of it's effects, and we know it's name, but we don't know why we always fall to the ground again every time we jump, we call that gravity, but still we don't know why...) or a conjecture (following the example: the existence of a particle that communicates the effect of gravity is conjectured)...

Is incredible the power science has to convince people that everything scientists say is absolutely right, however most scientific facts are probably false... everything is pure conjectures

Not true at all.

A hypothesis doesn't become a theory unless it accounts for all of the observed evidence. Not some of it. Not most of it. All of it.

It may end up being false all the same, but it will still provide an accurate explanation, it's just that the next theory provides an even more accurate one still.

Read Flatterland. All your dreams will come true.

Originally Posted by GDwarf

Not true at all.

A hypothesis doesn't become a theory unless it accounts for all of the observed evidence. Not some of it. Not most of it. All of it.

It may end up being false all the same, but it will still provide an accurate explanation, it's just that the next theory provides an even more accurate one still.

yeah... I know, I know... experimental proof and all... but as far as I know our 7 (or more) senses might be distorted, showing us things that aren't there, or aren't as we see, smell, hear, etc... them. (not that I think that's the case)

Besides, I'm a mathematician, so an experiment is no proof for me.

Of course I recognize the importance of theories, but they are just that: conjectures that haven't been proved wrong. in any case, most propositions about our universe cannot be proved (as there is no formal logical system beneath it).

I'm not trying to be super-skeptic, I'm just pointing out it's better not to believe what theories say "with all your heart", just to believe in their usefulness. They are analogies of the imaginary world to the real world, subject to change.

sorry if I'm making too much fuzz over nothing...

A considerable amount of physics is done using nothing but math, including pretty much everything done by Newton, Einstein, and Hawking, so presumably they shouldn't give you any believability problems.

On the contrary, it's because of the math...

if you study math, you become a little more skeptic...

they use some equations, just because they kind of work (between certain limits), but they are not shure why...

Still, most of modern physics is derived from a few base equations. Those equations have been shown to be as true as anything can be, so it's as solid a base as you can have.

(After all, if you don't trust observations, why would you trust math?)

They aren't as true as anything can be... 1.99 isn't equal to 2... even if it has 100 nines (only if it has infinite nines, but that's another story)... they are just models, approximations...

You cannot trust or not trust math in "real world things", because math for itself tells you nothing (about the universe)... it doesn't explain anything of the real world, it is it's own world. Other sciences (if you think math is a science) try to use mathematical models to explain phenomena of the real world, but math doesn't.

If I explain you the rules of chess and we start playing, you will probably trust me those are the "true" rules. if they aren't then we aren't playing chess, we are just playing another game and we changed it's name. but still, the rules are "true" for that other game, and we are still playing something. This happens a lot in mathematics, you think you discovered some new structures, but they were discovered a hundred years ago by someone else who gave them other names. Besides, in mathematics you make the laws, if you want 0=5 to be true (along with the field axioms, like conmutativity, existence of inverses, etc) then you will probably find a mathematical structure with those laws (it actually exists). So doing math is more like playing games, you invent the "rules", and then we try to find secondary rules derived from the first ones, and "strategies". Give me the axioms and I will give you theorems, which are true using this axioms, and might be false using other axioms... If you truly understand the rules of the game, then you will agree with other people who understand it, when you discuss what's a valid move and what's not valid. Sometimes the non-valid, or valid moves aren't all stated in the rules, just some of them, but the combination of this rules create other secondary rules that can be derived from the old ones, as I said before (axioms and theorems). You are never asked to "believe" the axioms, just to suppose they are true, and so, in mathematics there are no trusting problems.